This invention relates to the treatment of fly ash and other ash of a fine particulate nature, and in particular to its detoxification and/or re-use. The invention provides novel apparatus and methods for such treatment.
An object of the present invention is to treat toxic fly ash from incinerators, which ash is particulate, and other ash of particulate nature which can be retrieved, for example, from bottom ash of incinerators, and to convert such ash into a material which can be used, for example, in the construction industry. Throughout this specification, reference is made to fly ash, but this term is to be understood to include ash of fine particulate nature from any source of an incinerator, including bottom ash. In the UK the total toxic fly ash which is produced is approximately 200,000 tonnes/year from municipal incinerators alone. There is a major problem in the disposal of the fly ash/grit from an incinerator since it contains toxic, leachable heavy metals and organic materials such as dioxins. It is becoming more difficult and expensive to find landfill sites in which it is permitted to bury such material.
It has been proposed to heat fly ash to its fusion temperature in an arc furnace to form a fused slag which can be used for road making or for construction material purposes. Such processes, however, require a great deal of energy and are relatively inefficient.
GB-A-942620 discloses pelletising fly ash with a binder and then sintering the fly ash pellets on a moving grate. Nevertheless, this method requires a great deal of energy as well, not just to drive off the water binding the pellets together, but also to heat the inside of the pellets to effect internal sintering of the pellet ash. EP-A-0034389 discloses a similar process, as does JP-A-62256746. JP-A-3247541 appears to suggest settling fly ash on a moving grate and sintering it there.
JP-A-6351965 discloses a cyclone the inside of which is coated with sintered Titanium Dioxide.